1. Field of the Invention
The present invention relates to a precise grinding grindstone for grinding the surface of a hard brittle material such as glass or a semiconductive material with a satisfactory surface roughness, and a process for producing the same.
2. Related Background Art
Among such precise grinding grindstones, there are already known a grindstone in which plural layers of grinding particles are dispersed in a binder and fixed onto a substrate, and another grindstone in which a layer of grinding particles are fixed on a substrate by an electroplating process.
However, in such conventionally known grindstones, the one having plural layers of grinding particles dispersed in and fixed by the binder on the substrate shows unaligned end positions of the grinding particles because they are randomly supported in the binder. Also, the grindstone prepared by the electro-plating method has a layer of grinding particles fixed on the substrate, but the heights of the grinding particles are uneven, because of the unevenness in the size or shape of the grinding particles themselves. When the end positions of the grinding particles are unaligned, a high load is applied in the grinding operation to several grinding particles most protruding from the grindstone, thus providing a large cutting depth by such protruding several grinding particles.
In the grinding operation of a hard brittle article, the grinding is conducted in the shear mode if the cutting depth is less than a predetermined depth, and in the brittle mode if the cutting depth exceeds the predetermined depth. The predetermined cutting depth is called a critical cutting depth d.sub.c, which is an inherent value of the material. In the brittle-mode grinding, the article is ground with brittle breaking, and the ground surface becomes rougher than the desired surface roughness. Thus, when the cutting depth becomes larger and exceeds the critical depth d.sub.c, the work article is not ground with the shear mode indicating no brittle breaking but with the brittle mode, so that the desired surface roughness is hardly obtained.
The unevenness in the end heights of the grinding particles may be reduced by decreasing the size of the grinding particles, but, in such case, the amount of protrusion of the grinding particles becomes smaller, so that the gaps between the grinding particles will be easily clogged. Also, a smaller size of the grinding particles leads to a drawback that the particles tend to drop off due to a weakened holding force for the particles.